Air-conditioning system for vehicles

ABSTRACT

The present invention relates to an air-conditioning system for vehicles, in which expansion means and an internal heat exchanger are formed integrally with each other or expansion means, an internal heat exchanger and an accumulator are formed integrally with one another in an air-conditioning system using carbon dioxide (CO 2 ) as refrigerant so as to minimize and simplify a refrigerant line, thereby reducing the cost and a loss of energy according to a reduction in the number of assembly processes thereof. The air-conditioning system includes a compressor, a gas cooler, expansion means and an evaporator as a refrigerant line for circulating refrigerant in this order.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air-conditioning system for vehicles, and more particularly, to an air-conditioning system for vehicles, in which expansion means and an internal heat exchanger are formed integrally with each other or expansion means, an internal heat exchanger and an accumulator are formed integrally with one another in an air-conditioning system using carbon dioxide (CO₂) as refrigerant so as to minimize and simplify a refrigerant line, thereby reducing the cost and a loss of energy according to a reduction in the number of assembly processes thereof.

2. Background Art

In general, it has been widely known that CFC refrigerant called Freon gas destructs the ozone layer, and the CFC refrigerant rises as an environmental problem all over the world. Thus, in advanced countries, new alternative refrigerants, which can minimize the environmental problem, have been developed and applied to home appliances.

Among the alternative refrigerants, Carbon dioxide (CO₂) is has a merit in that it is easy in manufacturing a compact-sized air-conditioning system since it is a very stable, odorless, nontoxic, noncorrosive, unburned and nonexplosive material, compatible with lubricating oil, and is smaller in specific volume of gas than other refrigerants.

In addition, the greatest property of CO₂ is its high vapor pressure and low critical temperature.

Owing to the high vapor pressure and low critical temperature, a CO₂ refrigerant system has a supercritical cycle that absorbs heat at lower pressure than the critical pressure but emits heat at higher pressure (supercritical state) than the critical pressure. The CO₂ refrigerant system includes a compressor, a gas cooler, an internal heat exchanger, an expansion valve, an evaporator, and so on.

FIG. 1 is a configurative diagram of a CO₂ air-conditioning system having the above structure. In the CO₂ air-conditioning system, refrigerant is sequentially circulated in order of a compressor 5, a gas cooler 1, an internal heat exchanger 6, an expansion valve 2, an evaporator 3, an accumulator 4, the internal heat exchanger 6, and the compressor 5. Here, the accumulator 4 serves to remove liquid refrigerant contained in vapor refrigerant discharged from the evaporator 3 and supply only vapor refrigerant to the compressor 5.

Since efficiency of the supercritical refrigerant system is influenced by a control of an area of the gas cooler 1, it is necessary to control a refrigerant flow during throttling by detecting temperature and pressure of refrigerant of an outlet of the gas cooler 1. That is, the expansion valve 2 controls the refrigerant flow during throttling by detecting the temperature and pressure of the refrigerant of the outlet of the gas cooler 1 to keep proper temperature and pressure for the optimum efficiency of the system. Furthermore, in order to provide the optimum coefficient of performance, since the refrigerant temperature of the outlet of the gas cooler 1 must be lowest, the internal heat exchanger 6 is essentially needed to mutually heat-exchange the refrigerant of the outlet of the gas cooler 1 with refrigerant of an outlet of the evaporator 3.

The internal heat exchanger 6 heat-exchanges high-pressure refrigerant of the outlet of the gas cooler 1 with low-temperature and low-pressure refrigerant of the outlet of the evaporator 3 to thereby reduce enthalpy of refrigerant introduced into the expansion valve 2, whereby performance of the air-conditioning system can be maximized by increasing a difference in enthalpy between refrigerant of an inlet and refrigerant of the outlet of the evaporator 3 after a throttling process including an isenthalpic process. The low-temperature and low-pressure refrigerant is heated after passing through the accumulator 4 to raise the degree of superheat of an inlet of the compressor 5 and introduce liquid refrigerant to the inlet of the compressor 5, whereby a trouble of the compressor 5 can be prevented.

However, the conventional air-conditioning system for vehicles has a problem in that its manufacturing cost rises and a loss of energy is increased due to an extended and complicated refrigerant line since the expansion valve 2, the internal heat exchanger 6 and the accumulator 4 are separately connectively mounted on the refrigerant line.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior arts, and it is an object of the present invention to provide an air-conditioning system for vehicles, in which expansion means and an internal heat exchanger are formed integrally with each other or expansion means, an internal heat exchanger and an accumulator are formed integrally with one another in an air-conditioning system using carbon dioxide (CO₂) as refrigerant so as to minimize and simplify a refrigerant line, thereby reducing the cost and a loss of energy according to a reduction in the number of assembly processes thereof.

To accomplish the above object, according to the present invention, there is provided an air-conditioning system for vehicles, which comprises a compressor, a gas cooler, expansion means, and an evaporator as a refrigerant line for circulating refrigerant in this order, wherein the expansion means includes: an expansion block having a first high-pressure flow passage connected with an outlet line of the gas cooler and a second high-pressure flow passage connected with an inlet line of the evaporator; and an expansion valve mounted inside the expansion block and adapted to control the opening and closing degree of the second high-pressure flow passage according to temperature or pressure of refrigerant flowing in the first high-pressure flow passage, the air-conditioning system comprising an internal heat exchanger integrally mounted on a side of the expansion block and adapted to heat-exchange high-pressure refrigerant flowing from the first high-pressure flow passage to the second high-pressure flow passage with low-pressure refrigerant flowing from the evaporator to the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which:

FIG. 1 is a configurative diagram of a general air-conditioning system for carbon dioxide;

FIG. 2 is a configurative diagram of an air-conditioning system for vehicles according to a first preferred embodiment of the present invention;

FIG. 3 is a perspective view showing a state where expansion means and an internal heat exchanger are integrally formed in the air-conditioning system according to the first preferred embodiment of the present invention;

FIG. 4 is a sectional view taken along the line of A-A in FIG. 3;

FIG. 5 is a configurative diagram of an air-conditioning system for vehicles according to a second preferred embodiment of the present invention;

FIG. 6 is a perspective view showing a state where expansion means, an internal heat exchanger and an accumulator are integrally formed in the air-conditioning system according to the second preferred embodiment of the present invention; and

FIG. 7 is a sectional view showing the state where the expansion means, the internal heat exchanger and the accumulator are integrally formed in the air-conditioning system according to the second preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will be now made in detail to the preferred embodiment of the present invention with reference to the attached drawings.

In the present invention, description of the same configuration and action as the prior arts will be omitted.

FIG. 2 is a configurative diagram of an air-conditioning system for vehicles according to a first preferred embodiment of the present invention, FIG. 3 is a perspective view showing a state where expansion means and an internal heat exchanger are integrally formed in the air-conditioning system according to the first preferred embodiment of the present invention, and FIG. 4 is a sectional view taken along the line of A-A in FIG. 3.

As shown in the drawings, the air-conditioning system for vehicle according to the first preferred embodiment of the present invention uses carbon dioxide (CO₂) as refrigerant, and includes a compressor 10, a gas cooler 20, the expansion means 40/internal heat exchanger 49, an evaporator 30, and an accumulator 50 connected to a refrigerant line.

That is, refrigerant is circulated in order of the compressor 10, the gas cooler 20, the expansion means 40/internal heat exchanger 49, the evaporator 30, the accumulator 50, the expansion means 40/internal heat exchanger 49, and the compressor 10.

Here, the accumulator 50 is mounted between an outlet of the evaporator 30 and the internal heat exchanger 49, but may be omitted since it is selectively mounted.

In the air-conditioning system according to the present invention, the expansion means 40 and the internal heat exchanger 49 are formed integrally with each other, and so, the expansion means 40 will be described in detail.

The expansion means 40 includes an expansion block 41 and an expansion valve 40 a.

The expansion block 41 has uniform thickness and form, and includes a first high-pressure flow passage 52 connected with an outlet line 20 b of the gas cooler 20 and passing through both ends thereof, and a second high-pressure flow passage 43 spaced apart from the first high-pressure flow passage 42 at a predetermined interval and connected with an inlet line of the evaporator 30 a.

Here, the second high-pressure flow passage 43 is in an “L”-shaped form.

Moreover, an insertion hole 44 is formed inside the expansion block 41 for communicating the first high-pressure flow passage 42 with the second high-pressure flow passage 43 in such a way that the expansion valve 40 a can be inserted and mounted between the first and second high-pressure flow passages 42 and 43, and the expansion valve 40 a is inserted and mounted in the insertion hole 44.

The insertion hole 44 is formed at right angles to the first high-pressure flow passage 42 at a side thereof and penetrates from the side of the expansion block 41 to the second high-pressure flow passage 43 after passing through the first high-pressure flow passage 43 to thereby communicate the first and second high-pressure flow passages 42 and 43 with each other. Additionally, a sealing cap 40 d is mounted on the insertion hole 44 in such a way as to seal an entrance of the insertion hole 44 after the expansion valve 40 a is inserted and mounted therein, whereby a leakage of refrigerant from the expansion block 41 can be prevented.

Furthermore, the expansion valve 40 a is mounted in the insertion hole 44 of the expansion block 41, and controls the opening and closing degree of the second high-pressure flow passage 43 according to temperature or pressure of refrigerant flowing in the first high-pressure flow passage 42.

The expansion valve 40 a includes a temperature-sensing part 40 b adapted to perform contraction and expansion by sensing the temperature and pressure of the refrigerant flowing in the first high-pressure flow passage 42, and a valve part 40 c adapted to control the opening and closing degree of the second high-pressure flow passage 43 to adjust an amount of refrigerant supplied to the evaporator 30 according to the contraction or expansion of the temperature-sensing part 40 b.

In this instance, the temperature-sensing part 40 b is mounted on the first high-pressure flow passage 42 of the expansion block 41, and the valve part 40 c adjusts the amount of refrigerant passing through the second high-pressure flow passage 43 while vertically moving in interlock with the temperature-sensing part 40 b when the temperature-sensing part 40 b performs the contraction or expansion.

In addition, the second high-pressure flow passage 43 has flow passage reducing portions 43 a formed at upstream and downstream portions of the valve part 40 c for reducing a diameter of the flow passage, so that a throttling action can be performed smoothly during a process that the refrigerant passing through the second high-pressure flow passage 43 passes through the flow passage reducing portions 43 a.

In this instance, the flow passage reducing portions 43 a is formed adjacent to the valve part 40 c.

As described above, the expansion valve 40 a controls the opening and closing degree of the second high-pressure flow passage 43 according to the temperature or pressure of the refrigerant of the outlet of the gas cooler 20, which flows through the first high-pressure flow passage 42, to thereby adjust the flow amount of the refrigerant, whereby the system can keep a proper temperature or pressure to achieve the optimum efficiency.

Furthermore, the internal heat exchanger 49 is integrally mounted on a side of the expansion block 41, and heat-exchanges the high-pressure refrigerant flowing from the first high-pressure flow passage 42 to the second high-pressure flow passage 43 with the low-pressure refrigerant flowing from the evaporator 30 to the compressor 10.

Here, in case where the accumulator 50 is mounted between the evaporator 30 and the internal heat exchanger 49, the internal heat exchanger 49 heat-exchanges the high-pressure refrigerant flowing from the first high-pressure flow passage 42 to the second high-pressure flow passage 43 with the low-pressure refrigerant flowing from the accumulator 50 to the compressor 10.

Moreover, in order to mount the internal heat exchanger 49, the expansion block 41 includes a first low-pressure flow passage 45 connected with an outlet line 30 b of the evaporator 30 or an outlet line 50 b of the accumulator 50 (in case where the accumulator is mounted) and a second low-pressure flow passage 46 connected with an inlet line 10 a of the compressor 10.

In this instance, it is preferable that the second high-pressure flow passage 43 and the first low-pressure flow passage 45 are formed adjacent to a side of the expansion block 41. That is, when the second high-pressure flow passage 43 and the first low-pressure flow passage 45 are formed adjacent to the side of the expansion block 41, the side of the expansion block 41 can be directly mounted on inlet and outlet of the evaporator 30 and flow directions of the low-pressure refrigerant and the high-pressure refrigerant are opposed to each other in the internal heat exchanger 49 to thereby enhance a heat-exchanging performance.

The internal heat exchanger 49 includes: a low-pressure pipe 48 of a predetermined length mounted on a side of the expansion block 41 and adapted to communicatingly connect ah outlet of the first low-pressure flow passage 45 and an inlet of the second low-pressure flow passage 46 with each other; and a high-pressure pipe 47 of a predetermined length mounted on the side of the expansion block 41 and adapted to communicatingly connect an outlet of the first high-pressure flow passage 42 and an inlet of the second high-pressure flow passage 43 with each other.

That is, the internal heat exchanger 49 has a double pipe structure that the high-pressure pipe 47 is located inwardly and the low-pressure pipe 48 is located outwardly. In this instance, an end portion of the high-pressure pipe 47 is inserted into the first low-pressure flow passage 45 and connected with the outlet of the first high-pressure flow passage 42, and the other end portion is inserted into the second low-pressure flow passage 46 and connected with the inlet of the second high-pressure flow passage 43.

In the meantime, the first and second low-pressure flow passages 45 and 46 penetrating the expansion block 41 is not communicated with the first and second high-pressure flow passages 42 and 43, but communicated only with the low-pressure pipe 48.

In addition, the high-pressure pipe 47 and the low-pressure pipe 48 of the internal heat exchanger 49 can be bonded integrally with the expansion block 41 via welding, or coupled to the expansion block 41 through a separate sealing structure using an O-ring.

Accordingly, the high-temperature and high-pressure refrigerant discharged from the gas cooler 20 and flowing in the high-pressure pipe 47 through the first high-pressure flow passage 42 heat-exchanges with the low-temperature and low-pressure refrigerant discharged from the evaporator 30 or the accumulator 50 (in case where the accumulator 50 is mounted) and flowing in the low-pressure pipe 48 through the first low-pressure flow passage 45, whereby temperature of the high-temperature and high-pressure refrigerant before throttling lowers and the degree of superheat of the refrigerant introduced into the compressor 10 rises.

Additionally, the refrigerant heat-exchanged while flowing in the high-pressure pipe 47 is throttled while passing through the second high-pressure flow passage 43, and then, introduced into the evaporator 30. In this instance, the refrigerant heat-exchanged while flowing in the low-pressure pipe 48 passes through the second low-pressure flow passage 46, and then, is introduced into the compressor 10.

Hereinafter, a refrigerant circulation process of the air-conditioning system according to the first preferred embodiment will be described as follows.

First, when the high-temperature and high-pressure liquid refrigerant discharged from the compressor 10 is introduced into the gas cooler 20, the gas cooler 20 heat-exchanges the introduced liquid refrigerant with the outside air.

Continuously, the refrigerant passing through the gas cooler 20 is introduced into the first high-pressure flow passage 42 of the expansion block 41 through the outlet line 20 b of the gas cooler 20, and then, introduced into the second high-pressure flow passage 43 through the high-pressure pipe 47 of the internal heat exchanger 49.

The refrigerant introduced into the second high-pressure flow passage 43 is quickly expanded by the throttling action of the expansion valve 40 a and changed into a wet saturated state of low-temperature and low-pressure, and then, introduced into the evaporator 30 through the inlet line 30 a of the evaporator 30.

Thereafter, the evaporator 30 heat-exchanges the introduced refrigerant with air blown to the inside of the vehicle by a blower (not shown). In this instance, the refrigerant is evaporated in the evaporator 30 to thereby be converted into low-temperature and low-pressure refrigerant, and then, discharged to the outside.

After the liquid refrigerant is removed from the low-temperature and low-pressure refrigerant while the low-temperature and low-pressure refrigerant discharged from the evaporator 30 passes through the accumulator 50 along the outlet line 30 b of the evaporator 30, the refrigerant is introduced into the first low-pressure flow passage 45 of the expansion block 41 through the outlet line 50 b of the accumulator 50.

Thereafter, the refrigerant introduced into the first low-pressure flow passage 45 of the expansion block 41 is introduced into the second low-pressure flow passage 46 through the low-pressure pipe 48 of the internal heat exchanger 49.

In the above process, the high-temperature and high-pressure refrigerant passing through the high-pressure pipe 47 of the internal heat exchanger 49 heat-exchanges with the low-temperature and low-pressure refrigerant passing through the low-pressure pipe 48 of the internal heat exchanger 49, whereby temperature of the high-temperature and high-pressure refrigerant flowing from the gas cooler 20 to the expansion valve 40 a (valve part of the expansion valve) lowers and the degree of superheat of the low-temperature and low-pressure refrigerant introduced into the compressor 10 is kept properly.

In succession, the refrigerant discharged through the second low-pressure flow passage 46 is sucked to the compressor 10 through the inlet line 10 a of the compressor 10, and re-circulated in the same refrigerant cycle as the above.

FIG. 5 is a configurative diagram of an air-conditioning system for vehicles according to a second preferred embodiment of the present invention, FIG. 6 is a perspective view showing a state where expansion means, an internal heat exchanger and an accumulator are integrally formed in the air-conditioning system according to the second preferred embodiment of the present invention, and FIG. 7 is a sectional view showing the state where the expansion means, the internal heat exchanger and the accumulator are integrally formed in the air-conditioning system according to the second preferred embodiment of the present invention. In the second preferred embodiment of the present invention, only different parts from the first preferred embodiment will be described, and repeated description will be omitted.

As shown in the drawings, in the air-conditioning system for vehicles according to the second preferred embodiment, the expansion means 60, the internal heat exchanger 49 and the accumulator 50 are all integrally formed. That is, in the second preferred embodiment, the internal heat exchanger 49 is disposed integrally with a side of the expansion means 60 including an expansion valve 40 a and an expansion block 41 a, and the accumulator 50 is mounted in the internal heat exchanger 49.

So, refrigerant in the air-conditioning system according to the second preferred embodiment is circulated in order of a compressor 10, a gas cooler 20, the expansion means 60/internal heat exchanger 49/accumulator 50, an evaporator 30, the expansion means 40/internal heat exchanger 49/accumulator 50, and the compressor 10.

First, the expansion block 41 a has the same structure as the expansion block 41 of the first preferred embodiment within a range to first and second high-pressure flow passages 42 and 43 and an insertion hole 44. However, in the second preferred embodiment, since the accumulator 50 is mounted in the internal heat exchanger 49, a first low-pressure flow passage 45 a formed in the expansion block 41 a serves as a passageway to connect an outlet line 30 b of the evaporator 30 with the accumulator 50, and the expansion block 41 a in the second preferred embodiment does not have the second low-pressure flow passage 46, which is formed on the expansion block 41 and connected with the inlet line 10 a of the compressor 10 in the first preferred embodiment.

Of course, a second low-pressure flow passage 46 a is formed on an outlet of a low-pressure tank 48 a, which will be described later, and connected with the inlet line 10 a of the compressor 10.

That is, the first and second low-pressure flow passages 45 a and 46 a correspond with the first and second low-pressure flow passages 45 and 46 of the first preferred embodiment, and the low-pressure tank 48 a of the internal heat exchanger 49 of the second preferred embodiment corresponds with the low-pressure pipe 48 of the internal heat exchanger 49 of the first preferred embodiment.

Furthermore, the internal heat exchanger 49 includes: the low-pressure tank 48 a integrally formed on a side of the expansion block 41 a in such a way that the accumulator 50 connected with the outlet line 30 b of the evaporator 30 through the first low-pressure flow passage 45 a formed in the expansion block 41 a is mounted therein, the low-pressure tank 48 a having the second low-pressure flow passage 46 a formed on an outlet thereof in such a way that the refrigerant discharged from the accumulator 50 flows to the inlet line 10 a of the compressor 10; and a high-pressure pipe 47 adapted to connect an outlet of the first high-pressure flow passage 42 with an inlet of the second high-pressure flow passage 43 and wound on the outer peripheral surface of the accumulator 50 within the low-pressure tank 48 a, so that the internal heat exchanger 49 heat-exchanges low-pressure refrigerant flowing in the low-pressure tank 48 a and high-pressure refrigerant flowing in the high-pressure pipe 47 with each other.

That is, as you can see through the structure of the internal heat exchanger 49 according to the second preferred embodiment, the low-pressure tank 48 a, which connects the first and second low-pressure flow passages 45 a and 46 a with each other, surrounds the high-pressure pipe 47, which connects the first and second high-pressure flow passages 42 and 43 with each other, whereby the refrigerant flowing in the high-pressure pipe 47 is heat-exchanged with the refrigerant flowing in the low-pressure tank 48 a. Such a structure can be obtained by applying the structure of the internal heat exchanger 49 of the first preferred embodiment as it is.

In the meantime, the high-pressure pipe 47 is wound on the accumulator 50 ranging from the top to the bottom of the accumulator 50, and then, connected with the inlet of the second-high-pressure flow passage 43 through a receiving hole 51 a vertically formed in a vapor-liquid separation tank 51 of the accumulator 50.

Moreover, the accumulator 50 includes: the vapor-liquid separation tank 51 having an empty inside; an inflow pipe 52 adapted to communicate the first low-pressure flow passage 45 a formed in the expansion block 41 a with the inside upper portion of the vapor-liquid separation tank 51 to thereby introduce the low-pressure refrigerant discharged from the evaporator 30 into the vapor-liquid separation tank 51; a vapor-liquid separation plate 54 integrally formed on the lower end of the inflow pipe 52 for separating the liquid refrigerant and the vapor refrigerant by scattering the low-pressure refrigerant introduced through the inflow pipe 52; and an outflow pipe 53 adapted to communicate the inside upper portion of the vapor-liquid separation tank 51 with the inside of the low-pressure tank 48 a for discharging the vapor refrigerant of the vapor-liquid separation tank 51 to the inside of the low-pressure tank 48 a.

Meanwhile, the refrigerant introduced into the vapor-liquid separation tank 51 through the inflow pipe 52 is scattered by colliding with the vapor-liquid separation plate 54, and so, the liquid refrigerant contained in the refrigerant drops down along the inner wall surface of the vapor-liquid separation tank 51 and is gathered on the bottom of the vapor-liquid separation tank 51. In this instance, the liquid refrigerant gathered on the bottom of the vapor-liquid separation tank 51 contains also lubricating oil. While oil is generally soluble in and mixed with refrigerant, it is gathered on a position lower than that of the liquid refrigerant when the temperature is low since specific gravity of the liquid refrigerant is higher than oil.

Therefore, the inside of the vapor-liquid separation tank 51 is divided into an oil layer, a liquid refrigerant layer and a vapor refrigerant layer from the bottom thereof. In this instance, it is preferable that the outflow pipe 53 is in a “U”-shaped form as shown in the drawing and an inlet of the outflow pipe 53 is located in an area of the vapor refrigerant layer. It is also preferable that a bent lower end portion of the outflow pipe 53 is located in an area of the oil layer. Furthermore, it is preferable that an outlet of the outflow pipe 53 is formed at the top of the vapor-liquid separation tank 51, namely, opposed to the second low-pressure flow passage 46 a.

Moreover, in order to return the oil gathered on the bottom of the vapor-liquid separation tank 51 to the compressor 10, the outflow pipe 53 includes an oil hole 53 a formed on the lower end portion of the outflow pipe 53, which is located in the area of the oil gathered on the bottom of the vapor-liquid separation tank 51, and a filter 53 b mounted around the oil hole 53 a for preventing an inflow of foreign matters. So, the oil gathered on the bottom of the vapor-liquid separation tank 51 is introduced into the outflow pipe 53 through the oil hole 53 a, discharged to the inside of the low-pressure tank 48 a together with the vapor refrigerant flowing in the outflow pipe 53, and then, supplied to the compressor 10 through the second low-pressure flow passage 46 a.

As described above, in the second preferred embodiment, since the accumulator 50 is mounted in the low-pressure tank 48 a integrally formed on the side of the expansion block 41 a and the high-pressure pipe 47 is wound on the accumulator 50, the high-pressure pipe 47 and the low-pressure tank 48 a (which provides the same role as the low-pressure pipe of the first preferred embodiment) provide the same role as the internal heat exchanger 49 of the double pipe structure according to the first preferred embodiment, whereby the high-pressure refrigerant flowing in the high-pressure pipe 47 heat-exchanges with the low-pressure refrigerant flowing in the compressor 10 in the accumulator 50 through the low-pressure tank 48 a.

Accordingly, in the second preferred embodiment, since the expansion valve 40 a, the internal heat exchanger 49 and the accumulator 50 are formed integrally with one another, a size and a length of the refrigerant line is reduced more and a loss of energy can be reduced.

Hereinafter, a refrigerant circulation process of the air-conditioning system according to the second preferred embodiment will be described as follows.

First, when the high-temperature and high-pressure liquid refrigerant discharged from the compressor 10 is introduced into the gas cooler 20, the gas cooler 20 heat-exchanges the introduced liquid refrigerant with the outside air.

Continuously, the refrigerant passing through the gas cooler 20 is introduced into the first high-pressure flow passage 42 of the expansion block 41 through the outlet line 20 b of the gas cooler 20, and then, introduced into the second high-pressure flow passage 43 through the high-pressure pipe 47 of the internal heat exchanger 49.

The refrigerant introduced into the second high-pressure flow passage 43 is quickly expanded by the throttling action of the expansion valve 40 a and changed into a wet saturated state of low-temperature and low-pressure, and then, introduced into the evaporator 30 through the inlet line 30 a of the evaporator 30.

Thereafter, the evaporator 30 heat-exchanges the introduced refrigerant with air blown to the inside of the vehicle by a blower (not shown). In this instance, the refrigerant is evaporated in the evaporator 30 to thereby be converted into low-temperature and low-pressure refrigerant, and then, discharged to the outside.

The low-temperature and low-pressure refrigerant discharged from the evaporator 30 is introduced into the first low-pressure flow passage 45 a of the expansion block 41 a through the outlet line of the evaporator 30, and then, introduced into the vapor-liquid separation tank 51 of the accumulator 50 through the inflow pipe 52.

The refrigerant introduced into the vapor-liquid separation tank 51 is first collided with the vapor-liquid plate 54, and in this instance, the liquid refrigerant is gathered on the bottom of the vapor-liquid separation tank 51 while the vapor refrigerant and the liquid refrigerant are separated from each other, whereby only pure vapor refrigerant is discharged to the inside upper portion of the low-pressure tank 48 a through the outflow pipe 53.

Thereafter, the refrigerant discharged to the inside upper portion of the low-pressure tank 48 a flows to the lower portion of the low-pressure tank 48 a, and is discharged to the second low-pressure flow passage 46 a and introduced into the compressor 10 through the inlet line 10 a of the compressor 10.

In the above process, the high-temperature and high-pressure refrigerant passing through the high-pressure pipe 47 of the internal heat exchanger 49 heat-exchanges with the low-temperature and low-pressure refrigerant flowing in the low-pressure tank 48 a, whereby temperature of the refrigerant flowing from the gas cooler 20 to the expansion valve 40 a (valve part of the expansion valve) lowers and the degree of superheat of the refrigerant introduced into the compressor 10 from the accumulator 50 rises.

Here, since the high-pressure pipe 47 is wound on the vapor-liquid separation tank 51 of the accumulator 50, the high-temperature and high-pressure refrigerant flowing in the high-pressure pipe 47 heat-exchanges not only with the low-temperature and low-pressure refrigerant flowing in the accumulator 50 but also with the low-temperature and low-pressure refrigerant flowing in the low-pressure tank 48 a. Of course, the high-temperature and high-pressure refrigerant heat-exchanges with the low-temperature and low-pressure refrigerant flowing in the low-pressure tank 48 a more than the low-temperature and low-pressure refrigerant flowing in the accumulator 50.

Meanwhile, as described above, while only the air-conditioning system, which uses CO₂ as refrigerant, is described in the present invention, the present invention is not restricted to the above and is applicable to various air-conditioning systems, which use different refrigerants including an HFC-based refrigerant.

As described above, since the expansion means and the internal heat exchanger are formed integrally with each other or the expansion means, the internal heat exchanger and the accumulator are formed integrally with one another, the air-conditioning system according to the present invention can reduce the cost and the loss of energy by reducing the assembly process thereof through minimization and simplification of the refrigerant line.

In addition, since the expansion valve is embedded in the expansion block and the internal heat exchanger is integrally mounted on the side of the expansion block, the present invention can optimize efficiency thereof by adjusting the amount of the refrigerant introduced into the evaporator according to temperature and pressure of the refrigerant passing through the gas cooler.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention. 

1. An air-conditioning system for vehicles, which comprises a compressor, a gas cooler, expansion means and an evaporator as a refrigerant line for circulating refrigerant in this order, wherein the expansion means comprises: an expansion block having a first high-pressure flow passage connected with an outlet line of the gas cooler and a second high-pressure flow passage connected with an inlet line of the evaporator; and an expansion valve mounted inside the expansion block and adapted to control the opening and closing degree of the second high-pressure flow passage according to temperature or pressure of refrigerant flowing in the first high-pressure flow passage, the air-conditioning system comprising an internal heat exchanger integrally mounted on a side of the expansion block and adapted to heat-exchange high-pressure refrigerant flowing from the first high-pressure flow passage to the second high-pressure flow passage with low-pressure refrigerant flowing from the evaporator to the compressor.
 2. The air-conditioning system according to claim 1, wherein the expansion block includes a first low-pressure flow passage connected with an outlet line of the evaporator and a second low-pressure flow passage connected with an inlet line of the compressor.
 3. The air-conditioning system according to claim 2, wherein the internal heat exchanger includes: a low-pressure pipe of a predetermined length mounted on a side of the expansion block and adapted to connect an outlet of the first low-pressure flow passage and an inlet of the second low-pressure flow passage with each other; and a high-pressure pipe of a predetermined length mounted on the side of the expansion block in a double-pipe structure with the low-pressure pipe and adapted to connect an outlet of the first high-pressure flow passage and an inlet of the second high-pressure flow passage with each other, whereby the internal heat exchanger heat-exchanges low-pressure refrigerant flowing in the low-pressure pipe with high-pressure refrigerant flowing in the high-pressure pipe.
 4. The air-conditioning system according to claim 3, wherein the high-pressure pipe is mounted in the low-pressure pipe and has an end portion inserted into the first low-pressure flow passage and connected with the outlet of the first high-pressure flow passage and the other end portion inserted into the second low-pressure flow passage and connected with the inlet of the second high-pressure flow passage.
 5. The air-conditioning system according to claim 1, wherein the expansion block has an insertion hole formed between the first and second high-pressure flow passages for inserting the expansion valve thereto.
 6. The air-conditioning system according to claim 5, wherein a sealing cap is mounted on the insertion hole adapted to seal the insertion hole after the expansion valve is inserted and mounted into the insertion hole.
 7. The air-conditioning system according to claim 2, wherein the second high-pressure flow passage and the first low-pressure flow passage are formed adjacent to the side of the expansion block.
 8. The air-conditioning system according to claim 1, further comprising an accumulator mounted between an outlet of the evaporator and the internal heat exchanger.
 9. The air-conditioning system according to claim 1, wherein the expansion valve includes: a temperature-sensing part adapted to perform contraction and expansion by sensing temperature or pressure of the refrigerant; and a valve part adapted to control the opening and closing degree of the second high-pressure flow passage to adjust an amount of the refrigerant supplied to the evaporator according to the contraction or expansion of the temperature-sensing part.
 10. The air-conditioning system according to claim 1, wherein the temperature-sensing part is mounted on the first high-pressure flow passage of the expansion block.
 11. The air-conditioning system according to claim 1, wherein the internal heat exchanger includes: a low-pressure tank integrally formed on a side of the expansion block in such a way that the accumulator connected with the outlet line of the evaporator through the first low-pressure flow passage formed in the expansion block is mounted therein, the low-pressure tank having a second low-pressure flow passage formed on an outlet thereof in such a way that the refrigerant discharged from the accumulator flows to the inlet line of the compressor; and a high-pressure pipe adapted to connect an outlet of the first high-pressure flow passage with an inlet of the second high-pressure flow passage, the high-pressure pipe being wound on the outer peripheral surface of the accumulator within the low-pressure tank, whereby low-pressure refrigerant flowing in the low-pressure tank and high-pressure refrigerant flowing in the high-pressure pipe heat-exchange with each other.
 12. The air-conditioning system according to claim 11, wherein the accumulator includes: a vapor-liquid separation tank having an empty inside; an inflow pipe adapted to communicate the first low-pressure flow passage formed in the expansion block with the inside upper portion of the vapor-liquid separation tank to thereby introduce the low-pressure refrigerant discharged from the evaporator into the vapor-liquid separation tank; a vapor-liquid separation plate integrally formed on the lower end of the inflow pipe for separating the liquid refrigerant and the vapor refrigerant by scattering the low-pressure refrigerant introduced through the inflow pipe; and an outflow pipe adapted to communicate the inside upper portion of the vapor-liquid separation tank with the inside of the low-pressure tank for discharging the vapor refrigerant of the vapor-liquid separation tank to the inside of the low-pressure tank.
 13. The air-conditioning system according to claim 12, wherein an outlet of the outflow pipe is opposed to the second low-pressure flow passage.
 14. The air-conditioning system according to claim 2, further comprising an accumulator mounted between the outlet of the evaporator and the internal heat exchanger in such a way that an outlet line of the accumulator is connected with the first low-pressure flow passage. 